Add ability to have sub-chapters

This adds the ability for an RFC to have sub-chapters.

.github/workflows/deploy.yml

@@ -18,7 +18,7 @@ jobs:
         echo `pwd`/mdbook >> $GITHUB_PATH
     - name: Generate Book
       run: |
-        ./generate-book.sh
+        ./generate-book.py
     - name: Deploy GitHub Pages
       run: |
         git worktree add gh-pages gh-pages

generate-book.py

@@ -0,0 +1,60 @@
+#!/usr/bin/env python3
+
+"""
+This auto-generates the mdBook SUMMARY.md file based on the layout on the filesystem.
+
+This generates the `src` directory based on the contents of the `text` directory.
+
+Most RFCs should be kept to a single chapter. However, in some rare cases it
+may be necessary to spread across multiple pages. In that case, place them in
+a subdirectory with the same name as the RFC. For example:
+
+    0123-my-awesome-feature.md
+    0123-my-awesome-feature/extra-material.md
+
+It is recommended that if you have static content like images that you use a similar layout:
+
+    0123-my-awesome-feature.md
+    0123-my-awesome-feature/diagram.svg
+
+The chapters are presented in sorted-order.
+"""
+
+import os
+import shutil
+import subprocess
+
+def main():
+    if os.path.exists('src'):
+        # Clear out src to remove stale links in case you switch branches.
+        shutil.rmtree('src')
+    os.mkdir('src')
+
+    for path in os.listdir('text'):
+        symlink(f'../text/{path}', f'src/{path}')
+    symlink('../README.md', 'src/introduction.md')
+
+    with open('src/SUMMARY.md', 'w') as summary:
+        summary.write('[Introduction](introduction.md)\n\n')
+        collect(summary, 'text', 0)
+
+    subprocess.call(['mdbook', 'build'])
+
+def collect(summary, path, depth):
+    entries = [e for e in os.scandir(path) if e.name.endswith('.md')]
+    entries.sort(key=lambda e: e.name)
+    for entry in entries:
+        indent = '    '*depth
+        name = entry.name[:-3]
+        link_path = entry.path[5:]
+        summary.write(f'{indent}- [{name}]({link_path})\n')
+        maybe_subdir = os.path.join(path, name)
+        if os.path.isdir(maybe_subdir):
+            collect(summary, maybe_subdir, depth+1)
+
+def symlink(src, dst):
+    if not os.path.exists(dst):
+        os.symlink(src, dst)
+
+if __name__ == '__main__':
+    main()

generate-book.sh

@@ -1,22 +0,0 @@
-#!/usr/bin/env bash
-
-set -e
-
-if [ ! -d src ]; then
-    mkdir src
-fi
-
-printf '[Introduction](introduction.md)\n\n' > src/SUMMARY.md
-
-find text ! -type d -print0 | xargs -0 -I {} ln -fs ../{} src/
-
-find ./text ! -type d -name '*.md' -print0 \
-  | sort -z \
-  | while read -r -d '' file;
-do
-    printf -- '- [%s](%s)\n' "$(basename "$file" ".md")" "$(basename "$file")"
-done >> src/SUMMARY.md
-
-ln -fs ../README.md src/introduction.md
-
-mdbook build